Test: Colloids & Classification of Colloids (Old NCERT) - NEET MCQ

The size of colloidal particles is 10^-5 to 10^-7 cm which is intermediate between true solution and suspension.

Gas-gas is a true so|ution.

Liquid (water droplets) are dispersed in gas (air) in fog.

Gel is a colloidal system in which liquid is dispersed in a solid.

The gel is the colloid in which the dispersion phase is liquid and the dispersion medium is solid. Butter is an example of a gel.

Gel has liquid dispersed in solid.

If the dispersed phase is removed completely from the colloidal system, it can be formed again by mixing dispersion medium with it.

Lyophilic colloids are highly solvated hence more stable.

Lyophobic colloids cannot be prepared by simple mixing of dispersed phase and dispersion medium.

Lyophobic sols are irreversible while lyophilic sols are reversible.

Gold sol is a Lyophilic colloid.

At higher concentration the aggregated particles called micelles are formed by electrolytes like soap which act as colloidal particles.

In multimolecular colloids the smaller particles aggregate and are held together by van der Waal's forces. e.g., sols of gold atoms and sulphur molecules.

Substances whose molecules aggregate spontaneously in a given solvent to form particles of colloidal dimensions are called associated colloids or micells.

The formation of micelles takes place only above a particular temperature called Kraft  temperature (T_K).

CMC is the concentration below which no micellization takes place.

At CMC, the particles of an electrolyte aggregate and form associated colloids known as micelles.

The RCOO^- ion formed in the water contains two parts, a long hydrocarbon chain R (non-polar or hydrophobic tail) and a polar group COO^- (polar or hydrophilic head).

In lower concentration i.e., below critical micelle concentration (CMC) soap behaves like normal electrolytic solution.

White of an egg whipped with water acts as a macromolecular colloid.

Salt solution of gold is being reduced to gold by using a reducing agent like SnCl₂.

The method involves both dispersion and condensation. The intense heat of arc vapourises some of the metal which condenses under cold water.

Peptization involves conversion of freshly prepared precipitate into colloidal particles using a suitable electrolyte.

When an electric field is applied to purify an impure colloidal solution, the process is known as electrodialysis. The ions present in the colloidal solution migrate out to the oppositely charged electrodes.

Distillation cannot be used to remove impurities from colloidal sol.

Tyndall effect is observed only when these two conditions are satisfied.

The bright cone of the light is known as Tyndall cone. The scattering of light is seen by the microscope.

Tyndall effect is due to the scattering of light by colloidal particles. Sugar solution is a true homogeneous solution which will not show Tyndall effect.

Aqueous solution of Al(OH)₃ will show Tyndall effect since it is a colloidal solution. All other solutions are true solutions.

The colloidal particles are in a continuous zig-zag motion due to unbalanced bombardment of the particles by mole cules of the dispersion medium.